By Eric Levenson, CNN
(CNN) -- New York City began enforcing its Covid-19 vaccine passport program, known as "Key to NYC," for most indoor activities Monday as part of the city's broad reopening.
Since August 17, the city has required that people age 12 and older show proof they have had at least one Covid-19 vaccine dose for indoor dining, indoor fitness activities and indoor entertainment, including movie theaters, concert venues, museums and sports arenas. Enforcement of those rules began on Monday, the city said.
Businesses are now required to check the vaccination status of all staff and customers 12 and older, or they will be subject to fines. Residents can show proof of vaccination in the form of a CDC vaccination card, NYC vaccination record, the New York state Excelsior Pass or the NYC Covid Safe App.
Civilian inspectors from 13 city agencies were expected to begin the enforcement, Mayor Bill de Blasio said last week. These inspectors will be traveling to businesses to check that all procedures are being followed, that businesses have installed proper signage about the requirement, and that employees are properly checking for proof-of-vaccination, the mayor said.
The inspectors will be from 13 agencies, including the FDNY, the Department of Consumer Affairs, the Department of Buildings, the Department of Health, the Department of Transportation, the Department of Sanitation, the Department of Housing Preservation and Development, the NYC Sheriff's Office, the NYC Taxi and Limousine Commission, and the Parks Department.
The NYPD is not among the agencies providing civilian inspectors.
Even prior to the requirement, some indoor establishments in NYC had required proof of vaccination to enter.
The rule is part of the city's effort to vaccinate more people and thereby safely reopen the crowded city without sparking outbreaks of illness. As part of the incentive plan, the city offers $100 debit cards for anyone who gets a first vaccine dose as a metaphorical "carrot," while the "Key to NYC" program functions as the "stick" to punish those who are unvaccinated.
Monday also marked the first day of the school year for public schools -- this year with mask and vaccine requirements and no remote option -- and the return to work for many city employees.
"You can feel the life of the city," Mayor Bill de Blasio said Monday.
"This is the day we have been waiting for," he added. History will remember it as "a day that was a game changer, a difference maker, a turn around day. This is the day NYC's coming back in full force," he said.
The average daily number of new Covid-19 cases and the test positivity rate in New York City have both declined since a recent peak in late August, according to city data. Daily hospitalizations have also declined and are a fraction of the earlier surges last spring and last winter.
Still, the potential for dangerous outbreaks remains among pockets of unvaccinated people. City data shows that just over 79% of NYC adult residents have had at least one dose, including 86% of adults in Manhattan and Queens but 73% in Brooklyn.